Spring                                                     J. Brzozowski
Internet-Draft                                                  J. Leddy
Intended status: Informational                                   Comcast
Expires: October 15, 2017                                    C. Filsfils
                                                        R. Maglione, Ed.
                                                             M. Townsley
                                                           Cisco Systems
                                                          April 13, 2017

                         IPv6 SPRING Use Cases


   The objective of this document is to illustrate some use cases that
   need to be taken into account by the Source Packet Routing in
   Networking (SPRING) architecture in the context of an IPv6

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   This Internet-Draft will expire on October 15, 2017.

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   include Simplified BSD License text as described in Section 4.e of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IPv6 SPRING use cases . . . . . . . . . . . . . . . . . . . .   4
     2.1.  SPRING in the Home Network  . . . . . . . . . . . . . . .   4
     2.2.  SPRING in the Access Network  . . . . . . . . . . . . . .   5
     2.3.  SPRING in the Data Center . . . . . . . . . . . . . . . .   6
     2.4.  SPRING in the Content Delivery Networks . . . . . . . . .   6
     2.5.  SPRING in the Core networks . . . . . . . . . . . . . . .   7
   3.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Informative References  . . . . . . . . . . . . . . . . .   9
     7.2.  Normative References  . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Source Packet Routing in Networking (SPRING) architecture leverages
   the source routing paradigm.  An ingress node steers a packet through
   a controlled set of instructions, called segments, by prepending the
   packet with SPRING header.  The SPRING architecture is described in

   In today's networks, source routing is typically accomplished by
   encapsulating IP packets in MPLS LSPs that are signaled via RSVP-TE.
   Therefore, there are scenarios where it may be possible to run IPv6
   on top of MPLS, and as such, the MPLS Segment Routing architecture
   described in [I-D.ietf-spring-segment-routing-mpls] could be
   leveraged to provide spring capabilities in an IPv6/MPLS environment.

   However, there are other cases and/or specific network segments (such
   as for example the Home Network, the Data Center, etc.) where MPLS
   may not be available or deployable for lack of support on network
   elements or for an operator's design choice.  In such scenarios a
   non-MPLS based solution would be preferred by the network operators
   of such infrastructures.

   In addition there are cases where the operators could have made the
   design choice to disable IPv4, for ease of management and scale
   (return to single-stack) or due to an address constraint, for example
   because they do not possess enough IPv4 addresses resources to number

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   all the endpoints and other network elements on which they desire to
   run MPLS.

   In such scenario the support for MPLS operations on an IPv6-only
   network would be required.  However today's IPv6-only networks are
   not fully capable of supporting MPLS.  There is ongoing work in the
   MPLS Working Group, described in [RFC7439] to identify gaps that must
   be addressed in order to allow MPLS-related protocols and
   applications to be used with IPv6-only networks.  This is an another
   example of scenario where a solution relying on IPv6 without
   requiring the use of MPLS could represent a valid option to solve the
   problem and meet operators' requirements.

   It is important to clarify that today, it is possible to run IPv6 on
   top of an IPv4 MPLS network by using the mechanism called 6PE,
   described in [RFC4798].  However this approach does not fulfill the
   requirement of removing the need of IPv4 addresses in the network, as
   requested in the above use case.

   In summary there is a class of use cases that motivates an IPv6 data
   plane.  This document identifies some fundamental scenarios that,
   when recognized in conjunction, strongly indicate an IPv6 data plane:

   1.  There is a need or desire to impose source-routing semantics
       within an application or at the edge of a network (for example, a
       CPE or home gateway)

   2.  There is a strict lack of an MPLS dataplane in a portion of the
       end to end path

   3.  There is a need or desire to remove routing state from any node
       other than the source, such that the source is the only node that
       knows and will know the path a packet will take, a priori

   4.  There is a need to connect millions of addressable segment
       endpoints, thus high routing scalability is a requirement.  IPv6
       addresses are inherently summarizable: a very large operator
       could scale by summarizing IPv6 subnets at various internal
       boundaries.  This is very simple and is a basic property of IP
       routing.  MPLS node segments are not summarizable.  To reach the
       same scale, an operator would need to introduce additional
       complexity, such as mechanisms known with the industry term
       Seamless MPLS [I-D.ietf-mpls-seamless-mpls].

   In any environment with requirements such as those listed above, an
   IPv6 data plane provides a powerful combination of capabilities for a
   network operator to realize benefits in explicit routing, protection
   and restoration, high routing scalability, traffic engineering,

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   service chaining, service differentiation and application flexibility
   via programmability.

2.  IPv6 SPRING use cases

   This section will describe some scenarios where MPLS may not be
   present and it will highlight the need for the spring architecture to
   take them into account.

   The use cases described in the section do not constitute an
   exhaustive list of all the possible scenarios; this section only
   includes some of the most common envisioned deployment models for
   IPv6 Segment Routing.  In addition to the use cases described in this
   document the spring architecture should be able to be applied to all
   the use cases described in [RFC7855] for the spring MPLS data plane,
   when an IPv6 data plane is present.

2.1.  SPRING in the Home Network

   An IPv6-enabled home network provides ample globally routed IP
   addresses for all devices in the home.  An IPv6 home network with
   multiple egress points and associated provider-assigned prefixes
   will, in turn, provide multiple IPv6 addresses to hosts.  A homenet
   performing Source and Destination Routing
   ([I-D.ietf-rtgwg-enterprise-pa-multihoming]) will ensure that packets
   exit the home at the appropriate egress based on the associated
   delegated prefix for that link.

   A spring enabled home provides the ability to steer traffic into a
   specific path from end-hosts in the home, or from a customer edge
   router in the home.  If the selection of the source routed path is
   enabled at the customer edge router, that router is responsible for
   classifying traffic and steering it into the correct path.  If hosts
   in the home have explicit source selection rules, classification can
   be based on source address or associated network egress point,
   avoiding the need for DPI-based implicit classification techniques.
   If the traffic is steered into a specific path by the host itself, it
   is important to know which networks can interpret the spring header.
   This information can be provided as part of host configuration as a
   property of the configured IP address.

   The ability to steer traffic to an appropriate egress or utilize a
   specific type of media (e.g., low-power, WIFI, wired, femto-cell,
   bluetooth, MOCA, HomePlug, etc.) within the home itself are obvious
   cases which may be of interest to an application running within a
   home network.

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   Steering to a specific egress point may be useful for a number of
   reasons, including:

   o  Regulatory

   o  Performance of a particular service associated with a particular

   o  Cost imposed due to data-caps or per-byte charges

   o  Home vs. work traffic in homes with one or more teleworkers, etc.

   o  Specific services provided by one ISP vs. another

   Information included in the spring header, whether imposed by the
   end-host itself, a customer edge router, or within the access network
   of the ISP, may be of use at the far ends of the data communication
   as well.  For example, an application running on an end-host with
   application-support in a data center can utilize the spring header as
   a channel to include information that affects its treatment within
   the data center itself, allowing for application-level steering and
   load-balancing without relying upon implicit application
   classification techniques at the data-center edge.  Further, as more
   and more application traffic is encrypted, the ability to extract
   (and include in the spring header) just enough information to enable
   the network and data center to load-balance and steer traffic
   appropriately becomes more and more important.

2.2.  SPRING in the Access Network

   Access networks deliver a variety of types of traffic from the
   service provider's network to the home environment and from the home
   towards the service provider's network.

   For bandwidth management or related purposes, the service provider
   may want to associate certain types of traffic to specific physical
   or logical downstream capacity pipes.

   This mapping is not the same thing as classification and scheduling.
   In the Cable access network, each of these pipes are represented at
   the DOCSIS [DOCSIS] layer as different service flows, which are
   better identified as differing data links.  As such, creating this
   separation allows an operator to differentiate between different
   types of content and perform a variety of differing functions on
   these pipes, such as byte capping, regulatory compliance functions,
   and billing.

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   In a cable operator's environment, these downstream pipes could be a
   specific QAM [QAM], a DOCSIS [DOCSIS] service flow or a service

   Similarly, the operator may want to map traffic from the home sent
   towards the service provider's network to specific upstream capacity
   pipes.  Information carried in a packet's spring header could provide
   the target pipe for this specific packet.  The access device would
   not need to know specific details about the packet to perform this
   mapping; instead the access device would only need to know the
   interpretation of the spring header and how to map it to the target

2.3.  SPRING in the Data Center

   Some Data Center operators are transitioning their Data Center
   infrastructure from IPv4 to native IPv6 only, in order to cope with
   IPv4 address depletion and to achieve larger scale.  In such
   environment, source routing (through Segment Routing IPv6) can be
   used to steer traffic across specific paths through the network.  The
   specific path may also include a given function one or more nodes in
   the path are requested to perform.

   In addition one of the fundamental requirements for Data Center
   architecture is to provide scalable, isolated tenant networks.  In
   such scenario Segment Routing can be used to identify specific nodes,
   tenants, and functions and to build a construct to steer the traffic
   across that specific path.

2.4.  SPRING in the Content Delivery Networks

   The rise of online video applications and new, video-capable IP
   devices has led to an explosion of video traffic traversing network
   operator infrastructures.  In the drive to reduce the capital and
   operational impact of the massive influx of online video traffic, as
   well as to extend traditional TV services to new devices and screens,
   network operators are increasingly turning to Content Delivery
   Networks (CDNs).

   Several studies showed the benefits of connecting caches in a
   hierarchical structure following the hierarchical nature of the
   Internet.  In a cache hierarchy one cache establishes peering
   relationships with its neighbor caches.  There are two types of
   relationship: parent and sibling.  A parent cache is essentially one
   level up in a cache hierarchy.  A sibling cache is on the same level.
   Multiple levels of hierarchy are commonly used in order to build
   efficient caches architecture.

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   In an environment, where each single cache system can be uniquely
   identified by its own IPv6 address, a list containing a sequence of
   the caches in a hierarchy can be built.  At each node (cache) in the
   list, the presence of the requested content if checked.  If the
   requested content is found at the cache (cache hits scenario) the
   sequence ends, even if there are more nodes in the list; otherwise
   next element in the list (next node/cache) is examined.

2.5.  SPRING in the Core networks

   MPLS is a well-known technology widely deployed in many IP core
   networks.  However there are some operators that do not run MPLS
   everywhere in their core network today, thus moving forward they
   would prefer to have an IPv6 native infrastructure for the core

   While the overall amount of traffic offered to the network continues
   to grow and considering that multiple types of traffic with different
   characteristics and requirements are quickly converging over single
   network architecture, the network operators are starting to face new

   Some operators are looking at the possibility to setup an explicit
   path based on the IPv6 source address for specific types of traffic
   in order to efficiently use their network infrastructure.  In case of
   IPv6 some operators are currently assigning or plan to assign IPv6
   prefix(es) to their IPv6 customers based on regions/geography, thus
   the subscriber's IPv6 prefix could be used to identify the region
   where the customer is located.  In such environment the IPv6 source
   address could be used by the Edge nodes of the network to steer
   traffic and forward it through a specific path other than the optimal

   The need to setup a source-based path, going through some specific
   middle/intermediate points in the network may be related to different

   o  The operator may want to be able to use some high bandwidth links
      for specific type of traffic (like video) avoiding the need for
      over-dimensioning all the links of the network;

   o  The operator may want to be able to setup a specific path for
      delay sensitive applications;

   o  The operator may have the need to be able to select one (or
      multiple) specific exit point(s) at peering points when different
      peering points are available;

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   o  The operator may have the need to be able to setup a source based
      path for specific services in order to be able to reach some
      servers hosted in some facilities not always reachable through the
      optimal path;

   o  The operator may have the need to be able to provision guaranteed
      disjoint paths (so-called dual-plane network) for diversity

   All these scenarios would require a form of traffic engineering
   capabilities in IP core networks not running MPLS and not willing to
   run it.

3.  Contributors

   Many people contributed to this document.  The authors of this
   document would like to thank and recognize them and their
   contributions.  These contributors provided invaluable concepts and
   content for this document's creation.

      Ida Leung
      Rogers Communications
      8200 Dixie Road
      Brampton, ON  L6T 0C1

      Email: Ida.Leung@rci.rogers.com

      Stefano Previdi
      Cisco Systems
      Via Del Serafico, 200
      Rome  00142

      Email: sprevidi@cisco.com

      Christian Martin
      Cisco Systems

      Email: martincj@cisco.com

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4.  Acknowledgements

   The authors would like to thank Brian Field, Robert Raszuk, Wes
   George, Eric Vyncke, Fred Baker, John G.  Scudder and Yakov Rekhter
   for their valuable comments and inputs to this document.

5.  IANA Considerations

   This document does not require any action from IANA.

6.  Security Considerations

   This document presents use cases to be considered by the spring
   architecture and potential IPv6 extensions.  As such, it does not
   introduce any security considerations.  However, there are a number
   of security concerns with source routing at the IP layer [RFC5095].
   It is expected that any solution that addresses these use cases to
   also address any security concerns.

7.  References

7.1.  Informative References

   [DOCSIS]   "DOCSIS Specifications Page",

              Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
              M., and D. Steinberg, "Seamless MPLS Architecture", draft-
              ietf-mpls-seamless-mpls-07 (work in progress), June 2014.

              Baker, F., Bowers, C., and J. Linkova, "Enterprise
              Multihoming using Provider-Assigned Addresses without
              Network Prefix Translation: Requirements and Solution",
              draft-ietf-rtgwg-enterprise-pa-multihoming-00 (work in
              progress), March 2017.

              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-11 (work in progress), February

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              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-08
              (work in progress), March 2017.

   [QAM]      "QAM specification", <ITU-T Recommendation J.83 Annex B

   [RFC4798]  De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
              "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
              Provider Edge Routers (6PE)", RFC 4798,
              DOI 10.17487/RFC4798, February 2007,

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              DOI 10.17487/RFC5095, December 2007,

   [RFC7439]  George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for
              Operating IPv6-Only MPLS Networks", RFC 7439,
              DOI 10.17487/RFC7439, January 2015,

7.2.  Normative References

   [RFC7855]  Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
              Litkowski, S., Horneffer, M., and R. Shakir, "Source
              Packet Routing in Networking (SPRING) Problem Statement
              and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
              2016, <http://www.rfc-editor.org/info/rfc7855>.

Authors' Addresses

   John Brzozowski

   Email: john_brzozowski@cable.comcast.com

   John Leddy

   Email: John_Leddy@cable.comcast.com

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   Clarence Filsfils
   Cisco Systems

   Email: cfilsfil@cisco.com

   Roberta Maglione (editor)
   Cisco Systems
   Via Torri Bianche 8
   Vimercate  20871

   Email: robmgl@cisco.com

   Mark Townsley
   Cisco Systems

   Email: townsley@cisco.com

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